U.S. patent application number 12/774821 was filed with the patent office on 2010-12-09 for battery pack.
This patent application is currently assigned to SONY CORPORATION. Invention is credited to Kengo Ichimiya, Tetsuya Makino, Takehiko Tanaka, Masayuki Tohda, Masafumi Umekawa, Takeru Yamamoto.
Application Number | 20100310911 12/774821 |
Document ID | / |
Family ID | 43264023 |
Filed Date | 2010-12-09 |
United States Patent
Application |
20100310911 |
Kind Code |
A1 |
Yamamoto; Takeru ; et
al. |
December 9, 2010 |
BATTERY PACK
Abstract
A battery pack includes a plurality of batteries, each including
a battery element formed by winding or stacking a positive
electrode and a negative electrode with a separator therebetween,
and a packaging material packaging the battery element; a
connecting member that electrically connects the batteries to form
a battery group; a holding unit that holds the batteries together;
a protection circuit substrate connected to the battery group; and
an outer packaging member that integrally covers the battery group
and the protection circuit substrate, the outer packaging member
being formed by filling a space in a molding die housing the
battery group and the protection circuit substrate with a resin and
curing the resin at a temperature of 100.degree. C. or less.
Inventors: |
Yamamoto; Takeru;
(Fukushima, JP) ; Tanaka; Takehiko; (Fukushima,
JP) ; Tohda; Masayuki; (Fukushima, JP) ;
Makino; Tetsuya; (Fukushima, JP) ; Ichimiya;
Kengo; (Fukushima, JP) ; Umekawa; Masafumi;
(Fukushima, JP) |
Correspondence
Address: |
K&L Gates LLP
P. O. BOX 1135
CHICAGO
IL
60690
US
|
Assignee: |
SONY CORPORATION
Tokyo
JP
|
Family ID: |
43264023 |
Appl. No.: |
12/774821 |
Filed: |
May 6, 2010 |
Current U.S.
Class: |
429/94 |
Current CPC
Class: |
H01M 50/24 20210101;
H01M 10/0525 20130101; H01M 50/502 20210101; H01M 50/572 20210101;
H01M 50/557 20210101; Y02E 60/10 20130101; H01M 50/216 20210101;
H01M 50/116 20210101 |
Class at
Publication: |
429/94 |
International
Class: |
H01M 6/10 20060101
H01M006/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 3, 2009 |
JP |
P2009-134354 |
Claims
1. A battery pack comprising: a plurality of batteries, each
including a battery element formed by winding or stacking a
positive electrode and a negative electrode with a separator
therebetween, and a packaging material packaging the battery
element; a connecting member that electrically connects the
batteries to form a battery group; holding means for holding the
batteries together; a protection circuit substrate connected to the
battery group; and an outer packaging member that integrally covers
the battery group and the protection circuit substrate, the outer
packaging member being formed by filling a space in a molding die
housing the battery group and the protection circuit substrate with
a resin and curing the resin at a temperature of 100.degree. C. or
less.
2. The battery pack according to claim 1, wherein the resin of the
outer packaging member contains one resin selected from a urethane
resin, an acryl resin, and an epoxy resin.
3. The battery pack according to claim 1, wherein the resin of the
outer packaging member is a curable resin selected from a urethane
resin, an acryl resin, and an epoxy resin and contains an
endothermic agent composed of a compound that undergoes an
endothermic reaction.
4. The battery pack according to claim 2, wherein the resin of the
outer packaging member has an elongation of 5% or more and 40% or
less according to Japanese Industrial Standard K-7113.
5. The battery pack according to claim 2, wherein the resin of the
outer packaging member has a deflection temperature of 60.degree.
C. or more under a 0.45 MPa load according to Japanese Industrial
Standard K-7191 or has a glass transition temperature (Tg) of
55.degree. C. or more.
6. The battery pack according to claim 2, wherein the resin of the
outer packaging member contains one of an oxide containing Al or Si
and a nitride containing Al or Si.
7. The battery pack according to claim 1, wherein the packaging
material packaging the battery element is a film having at least
one layer and contains one of polyolefin and polyvinylidene
films.
8. The battery pack according to claim 3, wherein the compound
undergoes the endothermic reaction at a temperature in the range of
90.degree. C. to 150.degree. C.
9. The battery pack according to claim 8, wherein the compound that
undergoes the endothermic reaction contains at least one selected
from a hydroxide, a hydrate, a clathrate compound, a hydrate salt,
and a carbonate compound.
10. The battery pack according to claim 9, wherein the hydroxide is
a hydroxide of a metal selected from copper, zinc, aluminum,
cobalt, and nickel.
11. The battery pack according to claim 9, wherein the hydrate is a
hydrate of a metal selected from copper, zinc, aluminum, cobalt,
calcium, zirconium, nickel, and magnesium.
12. The battery pack according to claim 1, wherein the packaging
material for the battery element is an aluminum laminate film.
13. A battery pack comprising: a plurality of batteries, each
including a battery element formed by winding or stacking a
positive electrode and a negative electrode with a separator
therebetween, and a packaging material packaging the battery
element; a connecting member that electrically connects the
batteries to form a battery group; a holding unit that holds the
batteries together; a protection circuit substrate connected to the
battery group; and an outer packaging member that integrally covers
the battery group and the protection circuit substrate, the outer
packaging member being formed by filling a space in a molding die
housing the battery group and the protection circuit substrate with
a resin and curing the resin at a temperature of 100.degree. C. or
less.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] The present application claims priority to Japanese Priority
Patent Application JP 2009-134354 filed in the Japan Patent Office
on Jun. 3, 2009, the entire content of which is hereby incorporated
by reference.
BACKGROUND
[0002] The present application generally relates to a battery pack,
e.g., a battery pack including nonaqueous electrolyte secondary
batteries. In particular, the present application relates to a
battery pack that integrates a battery group and a protection
circuit substrate therefor, the battery group including a plurality
of batteries each including a battery element which is formed by
winding or stacking a positive electrode and a negative electrode
with a separator therebetween and which is packaged with a
packaging material.
[0003] Recently, a large number of portable electronic appliances
such as camcorders, cellular phones, portable computers, etc., have
emerged and the size and weight of these appliances are
increasingly reduced. As the electronic appliances become smaller
and more light-weight, the battery packs used as portable power
supplies for these electronic appliances are also desired to be
smaller and lighter and achieve high energy. One example of the
batteries used in such battery packs is high-capacity lithium ion
secondary batteries.
[0004] A lithium ion secondary battery includes a battery element
that includes a positive electrode and a negative electrode that
can be doped or dedoped with lithium ions. This battery element is
enclosed in a metal can or a metal laminate film and controlled by
a circuit substrate electrically connected to the battery element.
Some lithium ion secondary batteries of the related art are housed
together with circuit substrates in a casing that has an upper part
and a lower part so as to form a battery pack (refer to Japanese
Patent Nos. 3556875, 3614767, and 3643792).
SUMMARY
[0005] With regard to the lithium ion secondary batteries of the
related art described above, when metal cans are used to enclose
the battery elements, the thickness and weight tend to be large
although high dimensional accuracy can be easily achieved. In
contrast, when metal laminate films are used to enclose battery
elements, a higher volume energy density can be achieved and
thickness and weight can be reduced compared to when metal cans are
used. However, since dimensions of battery elements vary
significantly, it has been difficult to improve the dimensional
accuracy and the mechanical strength thereof has been low.
[0006] Also, in recent years, battery packs that integrate a
plurality of batteries are increasingly used. Examples thereof
include battery packs for automobiles using nickel hydride
batteries, which have already been put to practical use, and
battery packs for notebook computers and power tools. However,
since batteries in the battery packs undergo repeated expansion and
contraction with charge/discharge operation, the total amount of
deformation is not negligible although the amount of deformation of
individual batteries is small. Thus, in the related art, the only
viable option has been to use cylindrical batteries that do not
deform significantly. In such cases, however, large spaces exist
between batteries and thus the volume efficiency is low.
[0007] It is desirable to provide a battery pack that includes a
plurality of batteies having high volume energy density and that
has good dimensional accuracy and mechanical strength even when
rectangular batteries with high volume efficiencies are used
according to an embodiment.
[0008] An embodiment provides a battery pack including a plurality
of batteries, each including a battery element formed by winding or
stacking a positive electrode and a negative electrode with a
separator therebetween, and a packaging material packaging the
battery element; a connecting member that electrically connects the
batteries to form a battery group; a holding unit that holds the
batteries together; a protection circuit substrate connected to the
battery group; and an outer packaging member that integrally covers
the battery group and the protection circuit substrate, the outer
packaging member being formed by filling a space in a molding die
housing the battery group and the protection circuit substrate with
a resin and curing the resin at a temperature of 100.degree. C. or
less.
[0009] The resin of the outer packaging material preferably
contains one resin selected from a urethane resin, an acryl resin,
and an epoxy resin. More preferably, the resin is a curable resin
selected from a urethane resin, an acryl resin, and an epoxy resin
and contains an endothermic agent composed of a compound that
undergoes an endothermic reaction.
[0010] The inventors of the present application have found that
such a battery pack is suitable for automobile usages since it
suppresses battery deterioration, has good damping and impact
resistance properties, and is obtainable at lower cost.
[0011] In other words, according to this battery pack, a battery
element including a positive electrode, a negative electrode, and a
separator is hermetically sealed with a packaging material such as
a laminate film to form a battery. Then a battery group including a
plurality of such batteries is housed in a molding die and
integrated with a protection circuit substrate using a resin (outer
packaging member). Thus, the battery pack is free of contact
thermal resistance between minute heat insulating portions and
components.
[0012] When a resin having good thermal conductivity and a filler
are contained in the outer packaging member of the battery pack,
deterioration of some batteries caused by a uneven thermal
distribution can be significantly suppressed. When the capacities
of some of the batteries are deteriorated, other batteries become
overcharged, resulting in lithium precipitation and acceleration of
deterioration of other batteries, thereby creating a vicious cycle.
In contrast, the battery pack described above develops very little
uneveness of battery deterioration even after 1000 cycle
testing.
[0013] Disconnections of terminals, such as tabs, leads, etc., of
the batteries may occur in parts of circuits due to aged
deterioration and continuous vibrations and impacts. When
disconnection occurs, the electrical current that is supposed to
flow into batteries isolated by disconnection flows into the
batteries that remain connected. Thus, in such batteries that
remain connected, a current twice as large as the set current value
may flow. As a result, in electrochemically driven batteries,
unsafe operation conditions that cause lithium precipitation and
side reactions due to overcharging progress continuously, possibly
resulting in very serious battery deterioration and reliability
degradation. In contrast, the terminals of the battery pack
described above are extended from the batteries and fixed without
allowance. Thus, the failure mode mentioned above can be
avoided.
[0014] According to an embodiment, a battery pack that includes a
plurality of batteries having higher volume energy density than
batteries using metal cans can be provided. Even when rectangular
batteries having high volume efficiencies are used, a battery pack
with good dimensional accuracy and mechanical strength can be
provided. Moreover, the size and weight of the battery packs can be
reduced, and the safety and reliability can be further
improved.
[0015] Additional features and advantages are described herein, and
will be apparent from the following Detailed Description and the
figures.
BRIEF DESCRIPTION OF THE FIGURES
[0016] FIG. 1 is a perspective view illustrating the process of
assembling a battery;
[0017] FIG. 2 is a perspective view showing a structure of a
battery element;
[0018] FIG. 3A is a diagram showing a state before bending both
sides of a battery and FIG. 3B is a diagram showing a state after
bending both sides of the battery;
[0019] FIG. 4 is a cross-sectional view illustrating an embodiment
of a battery pack;
[0020] FIG. 5 is a front view of a battery including a battery
element packaged with a packaging material;
[0021] FIG. 6 is a diagram showing an example of a battery group in
which batteries are electrically connected to each other through
connecting members;
[0022] FIG. 7 is a diagram showing another example of a battery
group;
[0023] FIG. 8 is a diagram showing yet another example of a battery
group;
[0024] FIGS. 9A to 9E are plan views respectively showing examples
of holding units;
[0025] FIGS. 10A to 10C are perspective views illustrating the
process of producing a battery pack, from which illustration of
holding units is omitted; and
[0026] FIGS. 11A to 11C are perspective views illustrating the
process of producing battery packs using holding units.
DETAILED DESCRIPTION
[0027] The present application will now be described in detail with
reference to the drawings according to an embodiment. In this
description, the symbol "%" used to describe concentrations,
contents, filling ratios, etc., refers to percent by mass unless
otherwise noted.
[0028] A battery pack includes a plurality of batteries, connecting
members that electrically connect the batteries to each other to
form a battery group, a holding unit that holds the batteries
together, a protection circuit substrate connected to the battery
group, and an outer packaging material that integrally covers the
battery group, the protective circuit substrate, etc. Each of the
batteries includes a battery element formed by winding or stacking
a positive electrode and a negative electrode with separators
therebetween, and a packaging material covering the battery
element. The outer packaging material is formed by filling a space
in a molding die housing the battery group and the protection
circuit substrate with a resin and curing the resin at a
temperature of 100.degree. C. or less.
[0029] This battery pack has connecting members that electrically
connect the batteries to each other and a holding unit that holds
the batteries together, but does not need large-sized components
such as bus bars, base plates, and springs. Thus, the volume energy
density can be increased.
[0030] The battery element packaged with a packaging material has
dimensional tolerance derived from the coated area density of the
electrodes and the press density. The connecting member does not
have to be a common, firmly built bus bar constituted by a
plurality of components. A simple member that holds between the
terminals (tab leads) of the battery can be used as the connecting
member instead. This is because eventually a resin fills the space
beside the terminals and exhibits strength and an insulating
property once cured.
[0031] The holding unit may be a simple member designed on the
basis of the maximum dimensions of the battery because the holding
unit will eventually be integrated with an outer packaging member
(resin) and the strength and the pressure retention can be ensured.
The holding unit may be a member separate from a molding die, for
example, or may be a pin, a hook, a dent, a recess, or the like for
positioning integrated with the molding die. The holding unit not
only holds the batteries together but also fixes the battery group
onto the molding die. The molding die may be, for example, a resin
molding die constituted by a plurality of segments or a simple
casing.
[0032] According to a more preferred embodiment of the battery
pack, a resin in the outer packaging member may contain one of a
urethane resin, an acryl resin, and an epoxy resin. The resin in
the outer packaging member may be a curable resin selected from a
urethane resin, an acryl resin, and an epoxy resin and may contain
an endothermic agent containing a compound that undergoes
endothermic reactions.
[0033] The resin of the outer packaging member of the battery pack
preferably has an elongation of 5% or more and 40% or less
according to Japanese Industrial Standard (JIS) K-7113. When the
elongation is less than 5%, cracking readily occurs due to
vibrations or impacts; hence, in a long-term operation in which
expansion and contraction repeatedly occur in charge/discharge
cycles, the decrease in strength caused by similar local cracking
and changes in dimensions become problematic. When the elongation
exceeds 40%, expansion and contraction of batteries may not be
sufficiently suppressed and the interface between the positive and
negative electrodes may not be maintained.
[0034] The resin of the outer packaging member of the battery pack
preferably has a deflection temperature of 60.degree. C. or more
and 150.degree. C. or less under a load of 0.45 MPa according to
JIS K-7191, or a glass transition temperature (Tg) of 55.degree. C.
or more and 150.degree. C. or less.
[0035] The glass transition temperature (Tg) is preferably measured
on the basis of reaction delays, changes in elasticity (tan
.delta.) under deformation such as bending, stretching, or
shearing, or the like measured with a dynamic mechanical
spectrometer (DMS) so as to detect with high sensitivity the local
relaxations and the like of a polymeric material not detectable by
general thermal analysis. In these measurements, EXSTAR DMS6100, a
DMS produced by Seiko Instruments Inc., was used and bending
deformation was imparted such that the bending elasticity changed
from 10 to 120 MPa while the ambient environment temperature was
changed from 20.degree. C. to 200.degree. C. so as to estimate the
glass transition temperature (Tg) from the point of change in
elasticity. Alternatively, the glass transition temperature may be
determined by using the point of inflection determined by
differential scanning calorimetry (DSC) or the point of change in
coefficient of linear expansion determined by measuring the
elongation per degree Celsius of a solid having a unit length under
a particular pressure.
[0036] When the deflection temperature under load is lower than
60.degree. C. or the glass transition temperature is lower than
55.degree. C. and when the ambient temperature increases to near
60.degree. C., the toughness and viscosity rapidly decrease and the
outer packaging member becomes highly susceptible to deformation.
Thus, deformation may occur due to vibrations or impacts that occur
under typical operation conditions. Deformation also occurs due to
expansion and contraction accompanying charge/discharge operations.
Conversely, when the deflection temperature under load or the glass
transition temperature is over 150.degree. C., it takes a longer
time and a higher temperature for curing, resulting in a decrease
in productivity. In the case where the hardness of the outer
package remains unchanged up to 150.degree. C., ensuring sufficient
strength during normal operation may degrade safety since it may
suppress the quick splitting characteristic of polymer batteries at
a temperature under abnormal conditions.
[0037] The outer packaging member of the battery pack having the
above-described structure contains a shape-retaining polymer that
contains an insulating curable polyurethane resin containing a
polyol and a polyisocyanate.
[0038] In general, when a resin-containing material is used in the
outer packaging member, the outer packaging member is usually
formed by integrally covering the battery group and the protection
circuit substrate by using, for example, a die hot melting
technique. In this case, a thermoplastic resin that liquefies under
heating and re-solidifies under cooling or a curable resin that is
curable with, for example, heat is used.
[0039] However, since a thermoplastic resin develops fluidity after
being heated to a temperature 50.degree. C. to 150.degree. C.
higher than the melting point or the glass transition point (glass
transition temperature) of the resin, the thermoplastic resin is
usually heated to a high temperature of about 180.degree. C. to
450.degree. C. Curing of a thermoplastic resin starts the moment
the resin is injected into a die. Thus, in order to make a thin
molded product, the resin is supplied from a very narrow opening to
cover a large area, and this involves a process of injecting resin
that has a tendency to solidify in few seconds near the injection
port. Even when the resin is heated to a high temperature to
decrease the viscosity of the resin, even when the pressure of
injection is increased, or even when the number of injection ports
is increased, battery packs having a large area and a thickness of
250 .mu.m or less are difficult to obtain. In other words, only
battery packs having volume energy densities inferior to those
using metal cans can be fabricated when a resin is used in the
outer packaging member. On the other hand, when a thermosetting
resin of the related art is used, the curing temperature is as high
as about 150.degree. C. and the productivity is low because of a
long curing time.
[0040] Polyethylene-based separators commonly used in nonaqueous
electrolyte secondary batteries usually shut down at a temperature
of 120.degree. C. to 140.degree. C., turn into films that do not
allow ions to pass therethrough, and may no longer function as the
separators. The electrolytes (e.g., polyvinylidene fluoride used as
nonaqueous electrolytes) contained in the batteries may undergo
changes in physical properties, possibly resulting in deformation
of batteries.
[0041] A battery pack in which a battery group and a protection
circuit substrate are integrated has a positive temperature
coefficient (PCT) element built into the protection circuit so that
the PCT element functions as a controller in the event of abnormal
current flow. The term "positive temperature coefficient" means
that the electrical resistance of the PTC element increases with
the temperature and thus has a positive coefficient. However,
heating at such a high temperature may change the coefficient value
and may damage elements such as temperature thermal cutoffs, and
the protection circuit substrate may stop functioning as a
result.
[0042] According to the battery pack of one embodiment, an
insulating curable polyurethane resin containing a polyol and a
polyisocyanate is used as a shape-retaining polymer included in the
outer packaging member. Thus, the battery group and the protection
circuit can be integrally covered at relatively low temperatures
(e.g., 120.degree. C. or less), and a battery pack that achieves
high dimensional accuracy and high mechanical strength as well as
size and weight reduction can be provided without damaging the
battery group or the protection circuit substrate.
[0043] Since the outer packaging member containing the insulating
curable polyurethane resin is used, the dimensional accuracy is
improved. Thus, a battery pack made with the outer packaging member
is thinner than one using metal plates and exhibits higher yield
and improved energy density. Moreover, since the productivity and
the workability are improved by the use of this outer packaging
member, battery packs of various sizes, shapes, strengths, etc.,
suitable for various usages can be produced and the flexibility of
design can be increased.
[0044] Outer Packaging Member: Shape-Retaining Polymer
[0045] A shape-retaining polymer included in the outer packaging
material of a battery pack of one embodiment contains an insulating
curable polyurethane resin that contains a polyol and a
polyisocyanate. In this specification, the "insulating curable
polyurethane resin" refers to a material that yields a cured
product having a volume resistivity value (.OMEGA.cm) of
10.sup.10.OMEGA.cm or more measured at 25.+-.5.degree. C. and
65.+-.5% RH, and more preferably, a material that yields a cured
product having a volume resistivity value of 10.sup.11.OMEGA.cm or
more. The insulating curable polyurethane resin preferably yields a
cured product having a dielectric constant of 6 or less (1 MHz) and
a breakdown voltage of 15 kV/mm or more. The volume resistivity
value is measured according to JIS C2105 by measuring the value 60
seconds after starting application of a 500 V measurement voltage
to a sample (thickness: 3 mm) at 25.+-.5.degree. C. and 65.+-.5%
RH.
[0046] The polyol included in the insulating curable polyurethane
resin preferably has an oxygen content of 30% or less and more
preferably 20% or less. When the oxygen content of the polyol is
30% or less, the physical properties of the cured product obtained
therefrom do not readily change. The cured product exhibits high
moisture and heat resistance and an insulating property and is thus
suitable for use as the outer packaging member of the battery
pack.
[0047] The polyol included in the insulating curable polyurethane
resin preferably has an iodine number of 200 or less and more
preferably 150 or less. When the iodine value of the polyol used in
the shape-retaining polymer included in the outer packaging member
is 200 or less, the resulting cured product exhibits high thermal
resistance and becomes neither hard nor brittle even in a high
temperature environment. Thus, the cured product is suitable for
use as the outer packaging material that integrally covers the
battery group and the protection circuit substrate. The iodine
value is measured according to JIS K3331-1995.
[0048] The polyol included in the insulating curable polyurethane
resin is preferably a polyester polyol, a polyether polyol, or a
polyol having a main chain composed of carbon-carbon bonds, or a
mixture of these.
[0049] The polyester polyol is a reaction product of a fatty acid
and a polyol. The fatty acid may be at least one hydroxy-containing
long-chain fatty acid selected from the group consisting of
ricinoleic acid, oxycapronic acid, oxycapric acid, oxyundecanoic
acid, oxylinoleic acid, oxystearic acid, and oxyhexadecenoic acid.
The polyol reacting with the fatty acid may be at least one
selected from the group consisting of glycols such as ethylene
glycol, propylene glycol, butylene glycol, hexamethylene glycol,
and diethylene glycol, trifunctional polyols such as glycerin,
trimethylolpropane, and triethanolamine, tetrafunctional polyols
such as diglycerin and pentaerythritol, hexafunctional polyols such
as sorbitol, and octafunctional polyols such as maltose and
sucrose. Other examples thereof include addition polymers of
aliphatic, alicyclic, or aromatic amines and alkylene oxides
corresponding to these polyols and addition polymers of
polyamide-polyamine and such alkylene oxides.
[0050] In particular, ricinoleic acid glyceride, a polyester polyol
of ricinoleic acid and 1,1,1-trimethylolpropane, or the like is
preferably used.
[0051] The polyether polyol is composed of an addition polymer of
an alcohol and an alkylene oxide. The alcohol may be at least one
selected from the group consisting of ethylene glycol, diethylene
glycol, propylene glycol, dipropylene glycol, dihydric alcohols
such as 1,3-butanediol, 1,4-butanediol,
4,4'-dihydroxyphenylpropane, and 4,4'-dihydroxyphenylmethane, and
trihydric or higher alcohols such as glycerin,
1,1,1-trimethylolpropane, 1,2,5-hexanetriol, and pentaerythritol.
The alkylene oxide may be at least one selected from the group
consisting of ethylene oxide, propylene oxide, butylene oxide, and
.alpha.-olefin oxide.
[0052] The polyol having a main chain composed of carbon-carbon
bonds may be at least one selected from the group consisting of
acryl polyol, polybutadiene polyol, polyisoprene polyol,
hydrogenated polybutadiene polyol, polycarbonate polyol, a polyol
formed by grafting acrylonitrile (AN) or styrene monomer (SM) on a
polyol containing C--C bonds, and polytetramethylene glycol
(PTMG).
[0053] The polyol included in the insulating curable polyurethane
resin preferably contains a powder. When the polyol contains a
powder, the insulating curable polyurethane resin containing the
polyisocyanate and the polyol containing the powder exhibits good
thixotropy in integrally covering the battery group and the
protection circuit substrate and thereby improves the workability.
Moreover, since the polyol contains a powder, the outer packaging
member made of an insulating curable polyurethane resin containing
the polyisocyanate and the polyol containing the powder exhibits
improved surface hardness, heat resistance, and heat dissipating
property, etc.
[0054] Examples of the powder include inorganic particles such as
calcium carbonate, aluminum hydroxide, aluminum oxide, silicon
oxide, titanium oxide, silicon carbide, silicon nitride, calcium
silicate, magnesium silicate, and carbon, and organic polymer
particles such as polymethyl acrylate, polyethyl acrylate,
polymethyl methacrylate, polyethyl methacrylate, polyvinyl alcohol,
carboxymethyl cellulose, polyurethane, and polyphenol. These may be
used alone or in combination. Surfaces of the particles
constituting these powders may be surface-treated. The polyurethane
or polyphenol used as powders may be used as foamed powders.
Moreover, the powders may be porous.
[0055] The polyisocyanate included in the insulating curable
polyurethane resin is preferably an aromatic polyisocyanate, an
aliphatic polyisocyanate, or an alicyclic polyisocyanate, or a
mixture of these.
[0056] Examples of the aromatic polyisocyanate include
diphenylmethane diisocyanate (MDI), polymethylene polyphenylene
polyisocyanate (crude MDI), tolylene diisocyanate (TDI),
polytolylene polyisocyanate (crude TDI), xylene diisocyanate (XDI),
and naphthalene diisocyanate (NDI). Examples of the aliphatic
polyisocyanate include hexane methylene diisocyanate (HDI).
Examples of the alicyclic polyisocyanate include isophorone
diisocyanate (IPDI).
[0057] Other examples of the polyisocyanate include
carbodiimide-modified polyisocyanate produced by modifying the
aforementioned polyisocyanate with carbodiimide,
isocyanurate-modified polyisocyanate produced by modifying the
aforementioned polyisocyanate with isocyanurate, and
isocyanate-terminated urethane polymers produced by reaction
between a polyol and the polyisocyanate in excess. The
polyisocyanates may be used alone or in combination.
[0058] In particular, diphenylmethane diisocyanate, polymethylene
polyphenylene polyisocyanate, or carbodiimide-modified
polyisocyanate is preferably used.
[0059] A catalyst is added to the insulating curable polyurethane
resin to allow reactions between the polyol and the polyisocyanate
and promote dimerization and trimerization of isocyanates. Common
catalysts that catalyze the above-described reactions can be used
as the catalyst. Examples of the catalysts include amine-based
catalysts, metal-based isocyanuration catalysts, and organotin
compounds.
[0060] Examples of the amine-based catalyst include tertiary amines
such as triethylene diamine, 2-methyltriethylenediamine,
tetramethylhexanediamine, pentamethyldiethylenetriamine,
pentamethyldipropylenetriamine, pentamethylhexanediamine,
dimethylaminoethylether, trimethylaminopropylethanolamine,
tridimethylaminopropylhexahydrotriazine, and tertiary ammonium
salts.
[0061] Examples of the metal-based isocyanuration catalyst include
fatty acid metal salts such as dibutyltin dilaurate, lead octylate,
potassium ricinoleate, sodium ricinoleate, potassium stearate,
sodium stearate, potassium oleate, sodium oleate, potassium
acetate, sodium acetate, potassium naphthenate, sodium naphthenate,
potassium octylate, sodium octylate, and mixtures thereof.
[0062] A metal-based isocyanuration catalyst is preferably used
since isocyanurate rings can be introduced into the molecules of
the insulating curable polyurethane resin and the flame retardancy
and heat resistance of the cured product improve by the presence of
the isocyanurate rings. The metal-based isocyanuration catalyst is
preferably used in the range of 0.5 parts by weight or more and 20
parts by weight or less relative to 100 parts by weight of the
polyol. When the amount of the metal-based isocyanuration catalyst
is less than 0.5 parts by weight, sufficient isocyanuration does
not occur. When the amount of the metal-based isocyanuration
catalyst is more than 20 parts by weight relative to 100 parts by
weight of the polyol, the effect that corresponds to the amount
added is rarely achieved.
[0063] Examples of the organotin compound include tri-n-butyltin
acetate, n-butyltin trichloride, dimethyltin dichloride, dibutyltin
dichloride, and trimethyltin hydroxide. These catalysts may be used
as are or may be dissolved in a solvent such as ethyl acetate so
that the concentration thereof is in the range of 0.1 to 20%, and
then added so that the catalyst content in terms of solid is 0.01
to 5 parts by weight relative to 100 parts by weight of isocyanate.
Irrespective of whether the catalyst is added as is or as dissolved
in a solvent, the catalyst content in terms of solid is preferably
0.01 to 5 parts by weight and more preferably 0.05 to 1 part by
weight relative to 100 parts by weight of isocyanate. If the
catalyst content is excessively small, i.e., less than 0.01 parts
by weight, polyurethane resin molded article forms slowly and
molding becomes difficult since curing does not produce a resinous
matter. In contrast, when the catalyst content exceeds 5 parts by
weight, a resin is formed excessively fast and is thus difficult to
mold as a shape-retaining polymer included in the outer packaging
member of the battery pack.
[0064] The shape-retaining polymer used as the outer packaging
member of the battery pack may contain additives such as a filler,
a flame retarder, a defoaming agent, an antibacterial agent, a
stabilizer, a plasticizer, a thickner, an antifungal agent, another
resin, etc., in addition to the insulating curable polyurethane
resin as long as the curability is not degraded. For example,
triethyl phosphate, tris(2,3-dibromopropyl) phosphate, or the like
may be used as the flame retarder among the additives described
above. Examples of other additives include fillers such as antimony
trioxide and zeolite, and coloring materials such as dyes and
pigments.
[0065] Outer Packaging Member: Filler
[0066] The outer packaging member included in the battery pack
preferably contains, in addition to the shape-retaining polymer
described above, a filler that contains a metal oxide, a metal
nitride, or the like. Accordingly, the shape-retaining polymer
containing the insulating curable polyurethane resin preferably has
compatibility and reactivity with the filler. The shape-retaining
polymer more preferably has good adhesiveness with a metal laminate
film and good dimensional stability and moldability.
[0067] A ceramic filler, a metal oxide filler, or a metal nitride
filler may be used as the filler. Examples of the metal oxide
filler or the metal nitride filler include oxides or nitrides of
silicon (Si), aluminum (Al), titanium (Ti), zirconium (Zr), zinc,
(Zn), and magnesium (Mg) or any mixtures of the oxides or the
nitrides. These fillers composed of metal oxides or nitrides
improve hardness and thermal conductivity of the outer packaging
member. A layer containing a metal oxide filler or a metal nitride
filler may be disposed to be in contact with a layer containing the
shape-retaining polymer. Alternatively, the metal oxide filler or
the metal nitride filler may be mixed into the layer containing the
shape-retaining polymer. In such a case, the metal oxide filler or
the metal nitride filler is preferably evenly scattered over the
entire shape-retaining polymer layer.
[0068] The ratio at which the filler is mixed may be changed
depending on the type of the shape-retaining polymer but is
preferably 3 to 60% relative to the total mass of the
shape-retaining polymer. If the amount of filler is less than 3%,
an outer packaging member having a sufficient hardness may not be
obtained. If the amount of filler is more than 60%, problems
associated with moldability during production and brittleness of
the ceramic may arise.
[0069] When the average particle diameter of the filler is
decreased, the hardness increases but productivity may be degraded
since the decrease in average particle diameter affects the filling
property during molding. In contrast, when the average particle
diameter of the filler is increased, the desired strength may not
be obtained and the dimensional accuracy of the battery pack may
not be satisfactory. Thus, the average particle diameter of the
filler is preferably 0.5 to 40 .mu.m and more preferably 2 to 20
.mu.m.
[0070] The particles of the filler may take various shapes, such as
spherical, scale-like, plate-like, and needle-like shapes. Although
the shape of filler particles is not particularly limited,
spherical filler particles are preferable since spherical filler
particles with uniform average particle diameters can be produced
easily and are available at low cost. Needle-shaped filler
particles having high aspect ratios are also preferable since the
strength can be easily increased. The scale-shaped filler particles
are also preferred since the filling property can be increased when
the ratio of the filler mixed is high. Note that it is possible to
use filler particles having different average particle diameters
and shapes as a mixture according to the usage and the
material.
[0071] The outer packaging material may contain various other
additives in addition to the shape-retaining polymer and the filler
described above. For example, a curing agent, a UV absorber, a
photostabilizer, and any mixtures of these may be used in addition
to the shape-retaining polymer.
[0072] Characteristics of Outer Packaging Member
[0073] The battery pack of this embodiment uses the outer packaging
member containing the insulating curable polyurethane resin as the
shape-retaining polymer. This increases the dimensional accuracy,
impact resistance, and mechanical strength and reduces the size
(thickness) and the weight of the battery pack. This outer
packaging member preferably has the following physical property
values.
[0074] The glass transition point (Tg) of the outer packaging
member, which contains the insulating curable polyurethane resin
that serves as the insulating shape-retaining polymer, measured by
differential scanning calorimetry (DSC) is preferably 45 to
130.degree. C., more preferably 65 to 120.degree. C., and most
preferably 75 to 110.degree. C. The outer packaging member
preferably has good impact resistance and mechanical strength
during normal operation but is preferably easily breakable upon
occurrence of abnormal conditions so that the gas generated from
the battery can be easily discharged to the outside. A curable
polyurethane resin is preferably used as such a shape-retaining
polymer included in the outer packaging member. In order to satisfy
these requirements, the outer packaging member containing the
shape-retaining polymer preferably has a glass transition point
equal to or higher than the temperature at which the battery pack
is normally used but equal to or lower than the temperature at
which abnormal conditions occur. When the glass transition point is
less than 45.degree. C., the glass transition point of the outer
packaging member containing the shape-retaining polymer may become
lower than the temperature of normal use. This is not preferred
since it becomes difficult to suppress the thermal motion of
molecules constituting the shape-retaining polymer, to retain
curability, and to allow good mechanical strength to develop. In
contrast, when the glass transition point exceeds 130.degree. C.,
the glass transition point of the outer packaging member containing
the shape-retaining polymer may exceed the temperature at which
abnormal conditions occur. Thus, the thermal motion of molecules
constituting the shape-retaining polymer is suppressed under
abnormal conditions, the outer packaging member becomes not readily
breakable, and it becomes difficult for gas generated under
abnormal conditions to be rapidly discharged to the outside.
[0075] The flexural strength of the outer packaging member
containing the shape-retaining polymer determined by
Plastics--Determination of flexural properties according to JIS
K7171 is preferably 10 to 120 MPa, more preferably 20 to 110 MPa,
and most preferably 70 to 100 MPa.
[0076] The flexural modulus of the outer packaging member
containing the shape-retaining polymer determined by
Plastics--Determination of flexural properties according to JIS
K7171 is preferably 30 to 3000 MPa, more preferably 900 to 2550
MPa, and most preferably 1000 to 2500 MPa.
[0077] The outer packaging member containing the shape-retaining
polymer has a surface hardness of preferably D30 to D99, more
preferably D60 to D90, and most preferably D60 to D85 determined by
testing methods for durometer hardness of plastics according to JIS
K7215. When the durometer D hardness of the outer packaging member
is D30 to D99, an outer packaging member having high impact
resistance and mechanical strength can be obtained. The durometer D
hardness of the outer packaging member measured at a temperature
under abnormal conditions, e.g., 60.degree. C. or higher, is
preferably lower than the durometer D hardness of the outer
packaging member measured in a normal environment (temperature of
23.degree. C..+-.2.degree. C. and 50.+-.5% RH) prescribed in JIS
K7215. When the hardness of the outer packaging member at a
temperature under abnormal conditions is smaller than the hardness
under normal conditions, the gas generated under abnormal
conditions readily splits the outer packaging member and the gas
can be rapidly discharged to the outside in the event of splitting
of the outer packaging member.
[0078] The outer packaging member is thin. For example, the
thickness of the pack portion covering the largest area of a
rectangular battery for portable appliance usage is 1000 .mu.m or
less. When the thickness exceeds 1000 a battery pack made using
this outer packaging member may not fully exhibit advantages in
terms of volume energy density. More preferably, the thickness is
300 .mu.m or less. The thickness is preferably as small as possible
as long as the impact resistance and mechanical strength desirable
for the battery pack can be satisfied.
[0079] The combined use of the shape-retaining polymer and the
filler yields higher strength and higher impact resistance than the
use of aluminum metals or the combined use of a thermoplastic resin
and a metal in the related art. Thus, the same strength can be
achieved with smaller thickness, thereby increasing the volume
energy density. When the outer packaging member is thick, a battery
pack having a higher strength and higher reliability than the
related art can be obtained. Since the size and shape of the
battery can be relatively freely selected, the battery pack can be
applied to large-sized batteries such as backup power supplies of
bicycles and can be freely designed to fit in a desired place while
achieving a desired strength.
[0080] The resin of the outer packaging member of the battery pack
is preferably composed of one of the urethane resin, the acryl
resin, and the epoxy resin and preferably contains an endothermic
agent containing a compound that undergoes an endothermic reaction.
More preferably, the endothermic agent contains a compound that
undergoes an endothermic reaction in the range of 90 to 150.degree.
C.
[0081] Since a curable resin is used in this embodiment and the
endothermic compound can be added to the curable resin in a liquid
state before curing, the effect of suppressing temperature under
abnormal conditions can be achieved easily, in particular, without
increasing the number of production processes. Since the
endothermic compound can be added as a substitute for an inorganic
filler, the surface hardness of the resin can be improved and a new
effect of suppressing the swelling of the battery pack has been
confirmed by a high-temperature storage test at 60.degree. C.,
i.e., below the endothermic temperature. Since the appearance is
not affected, characters and the like may be laser-printed on the
resin surface to eliminate labels, thereby further improving the
volume energy density.
[0082] Examples of the endothermic agent include common endothermic
agents such as hydroxides, hydrates, clathrate hydrates such as
tetrahydrofuran (C.sub.4H.sub.8O.17H.sub.2O) and cyclodextrin,
hydrate salts such as sodium sulfate decahydrate, sodium
tetraborate decahydrate (Na.sub.2B.sub.4O.sub.7.10H.sub.2O), and
ammonium tetraborate tetrahydrate
((NH.sub.4).sub.2B.sub.4O.sub.7.4H.sub.2O), and carbonate
compounds.
[0083] The metal hydroxide preferably contains copper, zinc,
aluminum, cobalt, or nickel and may be any one of copper hydroxide,
zinc hydroxide, aluminum hydroxide, cobalt hydroxide, and nickel
hydroxide. In particular, copper hydroxide is preferred since it
causes dehydration and a reaction for generating a metal oxide at a
temperature of 100.degree. C. or higher and yields a large
endothermic effect.
[0084] The metal hydrate is preferably selected from metal hydrates
of copper, zinc, aluminum, cobalt, calcium, zirconium, nickel, and
magnesium. Preferred examples thereof include CuSO.sub.4.5H.sub.2O,
ZnSO.sub.4.H.sub.2O, ZnSO.sub.4.7H.sub.2O, AlCl.sub.3.6H.sub.2O,
aluminum silicate n-hydrate, (Al(NO.sub.3)3.9H.sub.2O), hydrates of
CoCl.sub.2 such as 1.5-hydrate, 2-hydrate, 4-hydrate, and 6-hydrate
of CoCl.sub.2, 2-hydrate, 4-hydrate, and 6-hydrate of CaCl.sub.2,
calcium silicate hydrate, calcium sulfate hydrate, zirconium
oxychloride octahydrate, zirconium oxynitrate dihydrate, zirconium
dioxide hydrate, nickel sulfate hexahydrate, nickel nitrate
hexahydrate, nickel chloride hexahydrate, magnesium sulfate
hydrate, magnesium fluoride hydrate, magnesium chloride
hexahydrate, bassanite (CaSO.sub.4.0.5H.sub.2O), and gypsum
(CaSO.sub.4.2H.sub.2O). Calcium sulfate (CaSO.sub.4.2H.sub.2O) that
starts endothermic reactions from at about 128.degree. C. and
calcium sulfite (CaSO.sub.3.2H.sub.2O) that starts endothermic
reactions at about 100.degree. C. are more preferable.
[0085] Any common carbonate salt can be used as the carbonate
compound. In particular, basic zinc carbonate is preferred since
its thermal decomposition temperature is about 120.degree. C. These
endothermic compounds may be used in combination with any compound
that has been used as a filler to increase the mechanical strength
and the flame retardancy.
[0086] The temperature at which endothermic reactions start
(a.k.a., onset temperature of endothermic reactions) was estimated
by differential scanning calorimetry (DSC). DSC6100 produced by SII
was used as the measuring instrument and a 20 mg of a sample was
weighed, sealed in an aluminum pan, and heated at 2.degree. C./min
from normal temperature to 600.degree. C., i.e., the melting point
of aluminum. The temperature at which the endothermic peak starts
was confirmed and this temperature was assumed to be onset
temperature of endothermic reactions.
[0087] The resin used in the outer packaging member of the battery
pack of this embodiment is preferably a thermosetting resin.
Alternatively, a thermoplastic resin, a curable resin that has
already been cured, a metal plate, or a metal component may be used
in part of the outer packaging member to improve the productivity,
the positioning accuracy, and the production takt time.
[0088] The thermoplastic resin may be any but is preferably
polyethylene, polypropylene, polyamide, or polycarbonate. From the
viewpoints of adhesiveness to the thermosetting resin, flame
retardancy, and mechanical strength, polyamide or polycarbonate is
more preferably used. The curable resin may be any but is
preferably an acryl resin, an epoxy resin, or a urethane resin.
More preferably, the same resin as the resin injected into a die is
used from the viewpoints of raw material cost, shared use of
production facilities, adhesive strength, etc.
[0089] Next, an embodiment of a battery pack is described with
reference to the drawings. A battery pack P shown in FIG. 4
includes a plurality of batteries 20, connecting members 31 that
electrically connect the batteries 20 to form a battery group G, a
holder 33A that holds the batteries 20 together, a protection
circuit substrate 32, and an outer packaging member 18 that
integrally covers the battery group G, the protection circuit
substrate 32, the holder 33A, and other associated components. The
outer packaging member 18 is formed by filling the space inside a
casing (molding die) C housing the battery group G and the
protection circuit substrate 32 with a resin and curing the resin
at a temperature of 100.degree. C. or less. The outer packaging
member 18 shown in the drawing integrally covers the battery group
G, the protection circuit substrate 32, and other associated
components while having terminals of the batteries 20 extended to
the outside.
[0090] The batteries 20 are nonaqueous electrolyte secondary
batteries and, as shown in FIG. 1, are each prepared by packaging a
battery element 10 with a metal laminate film 17, which is one
example of a packaging material. The battery element 10 is placed
in a recess 17a (space 17a) formed in the laminate film 17 and the
periphery of the battery element 10 is sealed. In this embodiment,
the space 17a is a rectangular space having a shape corresponding
to the rectangular shape of the battery element 10.
[0091] The packaging material for packaging the battery element 10
may be any common metal laminate film but is preferably an aluminum
laminate film. The aluminum laminate film is preferably one suited
for drawing and forming the recess 17a for housing the battery
element 10.
[0092] The packaging material for packaging the battery element 10
is preferably a film including at least one layer, and preferably
contains one of polyolefin and polyvinylidene. For example, a
multilayer laminate film including an aluminum layer and an
adhesive layer and a surface protection layer disposed on both
sides of the aluminum layer can be used as the aluminum laminate
film. An aluminum laminate film in which a propylene (PP) layer
serving as an adhesive layer, an aluminum layer serving as a metal
layer, and a nylon or polyethylene terephthalate (PET) layer
serving as the surface protection layer are arranged in that order
from the inside of the battery element 10, i.e., from the surface
side of the battery element 10 is preferably used as the aluminum
laminate film.
[0093] The structure of the battery element 10 will now be
described. FIG. 2 is a perspective view showing the structure of
the battery element 10 packaged and housed in the laminate film 17
serving as the packaging material. In the drawing, a strip-shaped
positive electrode 11, a separator 13a, a strip-shaped negative
electrode 12 disposed to oppose the positive electrode 11, and a
separator 13b are sequentially stacked and wound in the
longitudinal direction to form the battery element 10. Both sides
of the positive electrode 11 and the negative electrode 12 are
coated with a gel electrolyte 14.
[0094] A positive electrode terminal 15a that connects to the
positive electrode 11 and a negative electrode terminal 15b that
connects to the negative electrode 12 (hereinafter, these terminals
may be referred to as "electrode terminals 15" without designating
specific terminals to which they connect) are extended from the
battery element 10. The positive electrode terminal 15a and the
negative electrode terminal 15b are respectively coated with a
sealant 16a and a sealant 16b (hereinafter, the sealants may be
generally referred to as "sealants 16") which are resin pieces
composed of polypropylene modified with maleic anhydride (PPa) or
the like so as to improve the adhesiveness to the laminate film 17
provided later as a package.
[0095] The constitutional elements of the battery (before being
packaged with the outer packaging member) will now be described in
detail.
[0096] Positive Electrode
[0097] The positive electrode includes a positive electrode
collector and positive electrode active material layers disposed on
both sides of the positive electrode collector. The positive
electrode active material layers contain a positive electrode
active material. The positive electrode collector includes a metal
foil such as an aluminum (Al) foil. The positive electrode active
material layers contain, for example, a positive electrode active
material, a conductant agent, and a binder. The positive electrode
active material, the conductant agent, and the binder may be mixed
at any ratio as long as they can be homogeneously dispersed in a
solvent.
[0098] A metal oxide, a metal sulfide, or a particular polymer may
be used as the positive electrode active material according to the
type of the battery desired. For example, in order to construct a
lithium ion battery, a complex oxide of a transition metal and
lithium, represented by formula (I), may be used:
LiXMO.sub.2 (1)
[0099] (where M represents at least one transition metal and X
usually represents 0.05 to 1.10 although X varies depending on the
charge/discharge state of the battery.) Cobalt (Co), nickel (Ni),
manganese (Mn), etc., may be used as the transition metal (M) of
the lithium complex oxide.
[0100] Specific examples of the lithium complex oxide include
LiCoO.sub.2, LiNiO.sub.2, LiMn.sub.2O.sub.4, and
LiNi.sub.yCO.sub.1-yO.sub.2 (0<y<1). A solid solution having
some atoms of the transition metal element substituted with atoms
of a different element can also be used. Examples thereof include
LiNi.sub.0.5CO.sub.0.5O.sub.2 and LiNi.sub.0.8CO.sub.0.2O.sub.2.
These lithium complex oxides can generate high voltage and exhibit
high energy density. A metal sulfide or oxide that does not contain
lithium, such as TiS.sub.2, MoS.sub.2, NbSe.sub.2, and
V.sub.2O.sub.5 may be used as the positive electrode active
material. These positive electrode active materials may be used
alone or in combination.
[0101] A carbon material such as carbon black and graphite may be
used as the conductant agent, for example. Polyvinylidene fluoride,
polytetrafluoroethylene, polyvinylidene fluoride, etc., can be used
as the binder. N-methylpyrrolidone and the like can be used as the
solvent.
[0102] The positive electrode active material, the binder, and the
conductant agent are homogeneously mixed to prepare a positive
electrode mix, and this positive electrode mix is dispersed in a
solvent to prepare a slurry. The slurry is evenly applied on the
positive electrode collector by a doctor blade technique or the
like, dried under a high temperature to evaporate solvent, and
pressed to form positive electrode active material layers.
[0103] The positive electrode 11 includes the positive electrode
terminal 15a connected to one end of the positive electrode
collector by spot welding or ultrasonic welding. The positive
electrode terminal 15a is preferably a metal foil or a mesh but
does not have to be composed of a metal as long as the terminal is
electrochemically and chemically stable and conducts electricity.
Examples of the material for the positive electrode terminal 15a
include aluminum.
[0104] Negative Electrode
[0105] The negative electrode includes a negative electrode
collector and negative electrode active material layers disposed on
both sides of the negative electrode collector. The negative
electrode active material layers contain a negative electrode
active material. The negative electrode collector includes a metal
foil, e.g., a copper (Cu) foil, a nickel foil, or a stainless steel
foil.
[0106] The negative electrode active material layer contains, for
example, a negative electrode active material, a conductant agent
if desired, and a binder. The negative electrode active material,
the conductant agent, the binder, and the solvent may be mixed at
any ratio as with the positive electrode active material.
[0107] A carbon material or metal-carbon complex material that can
dope and dedope lithium metal, lithium alloys, or lithium can be
used as the negative electrode active material. Specific examples
of the carbon material that can dope and dedope lithium include
graphite, non-graphitizable carbon, and graphitizable carbon. More
specifically, carbon materials such as pyrolytic carbons, cokes
(pitch coke, needle coke, and petroleum coke), graphites, glassy
carbons, organic polymer compound sinters (produced by baking and
carbonizing a suitable resin such as a phenol resin or furan resin
at an appropriate temperature), carbon fibers, and activated carbon
can be used. A polymer such as polyacetylene, polypyrrole, etc., or
an oxide such as SnO.sub.2 can be used as the material that can
dope and dedope lithium.
[0108] Various types of metals can be used as a material that can
alloy with lithium. For example, tin (Sn), cobalt (Co), indium
(In), aluminum (Al), silicon (Si), and alloys of these are
frequently used. When metallic lithium is used, it is not always
necessary to use a metallic lithium powder and form the metallic
lithium powder into a coating film using a binder. Instead, rolled
lithium metal foils may be used and press-bonded onto the
collector.
[0109] Examples of the binder include polyvinylidene fluoride and
styrene butadiene rubber. For example, N-methylpyrrolidone or
methyl ethyl ketone can be used as the solvent.
[0110] The negative electrode active material, the binder, and the
conductant agent are homogeneously mixed to prepare a negative
electrode mix, and this negative electrode mix is dispersed in a
solvent to prepare a slurry. The slurry is evenly applied on the
negative electrode collector by a technique similar to that for
forming the positive electrode, dried under a high temperature to
evaporate the solvent, and pressed to form negative electrode
active material layers.
[0111] As with the positive electrode 11, the negative electrode 12
also includes a negative electrode terminal 15b connected to one
end of the collector by spot welding or ultrasonic welding. The
negative electrode terminal 15b does not have to be composed of a
metal as long as it is electrochemically and chemically stable and
conducts electricity. Examples of the material for the negative
electrode terminal 15b include copper and nickel.
[0112] When the battery element 10 has a rectangular shape, the
positive electrode terminal 15a and the negative electrode terminal
15b are preferably extended in the same direction from one side
(usually one of the short sides) of the battery element 10 as shown
in FIGS. 1 to 5. However, the direction in which the terminals are
extended may be any as long as shorting or the like does not occur
and the battery performance is not degraded. The positions to which
the positive electrode terminal 15a and the negative electrode
terminal 15b are connected may be any and the technique used for
establishing the connections may be any as long as electrical
contacts are achieved.
[0113] Electrolyte
[0114] An electrolyte salt and a nonaqueous solvent commonly used
for lithium ion batteries can be used as the electrolyte.
[0115] Examples of the nonaqueous solvent include ethylene
carbonate, propylene carbonate, .gamma.-butyrolactone, dimethyl
carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl
carbonate, ethyl propyl carbonate, and solvents prepared by
substituting hydrogen of the carbonic acid esters by a halogen.
These solvents may be used alone or as a mixture including a
plurality of types of solvents at a particular composition
ratio.
[0116] A material commonly used in battery electrolytes can be used
as the lithium salt, which is one example of the electrolyte salt.
Specific examples thereof include LiCl, LiBr, LiI, LiClO.sub.3,
LiClO.sub.4, LiBF.sub.4, LiPF.sub.6, LiNO.sub.3,
LiN(CF.sub.3SO.sub.2).sub.2, LiN(C.sub.2F.sub.5SO.sub.2).sub.2,
LiAsF.sub.6, LiCF.sub.3SO.sub.3, LiC(SO.sub.2CF.sub.3).sub.3,
LiAlCl.sub.4, and LiSiF.sub.6. From the viewpoint of oxidation
stability, LiPF.sub.6 and LiBF.sub.4 are preferred. These lithium
salts may be used alone or in combination as a mixture. The
concentration for dissolving the lithium salt may be any as long as
the lithium salt can be dissolved in the nonaqueous solvent. The
lithium ion concentration is preferably in the range of 0.4 mol/kg
to 2.0 mol/kg relative to the nonaqueous solvent.
[0117] When a gel electrolyte is used, the electrolyte described
above is gelled with a matrix polymer. The matrix polymer may be
any polymer that is compatible with the nonaqueous electrolytic
solution prepared by dissolving the electrolyte salt in the
nonaqueous solvent and that can be gelled. Examples of the matrix
polymer include polymers that contain polyvinylidene fluoride,
polyethylene oxide, polypropylene oxide, polyacrylonitrile, and
polymethacrylonitrile in the repeating units. These polymers can be
used alone or in combination.
[0118] In particular, polyvinylidene fluoride and a copolymer in
which 7.5% or less of hexafluoropropylene is introduced into
polyvinylidene fluoride are preferred as the matrix polymer. Such a
polymer usually has a number-average molecular weight in the range
of 5.0.times.10.sup.5 to 7.0.times.10.sup.5 (500 thousand to 700
thousand) or a weight-number molecular weight in the range of
2.1.times.10.sup.5 to 3.1.times.10.sup.5 (210 thousand to 310
thousand), and an intrinsic viscosity in the range of 1.7 to 2.1
dl/g.
[0119] Separator
[0120] The separator is made of a porous film composed of an
inorganic material, such as a ceramic nonwoven cloth or a porous
film composed of a polyolefin material such as polypropylene (PP)
or polyethylene (PE) and may have a multilayer structure including
two or more types of these porous films. Of these, porous films
composed of polyethylene or polypropylene are most effective.
[0121] In general, a separator having a thickness of 5 to 50 .mu.m
is suitable for use. The thickness is more preferably 7 to 30
.mu.m. If the separator is excessively thick, the filling ratio of
the active material decreases, thereby decreasing the battery
capacity and ion conductivity and degrading the current
characteristics. If the separator is excessively thin, the
mechanical strength of the film decreases.
[0122] Production of Battery
[0123] The gel electrolyte solution prepared as above is evenly
applied onto the positive electrode 11 and the negative electrode
12 to impregnate the positive electrode active material layer and
the negative electrode active material layer, and either stored at
normal temperature or subjected to a drying step to form gel
electrolyte layers 14.
[0124] Next, the positive electrode 11 provided with the gel
electrolyte layers 14, the separator 13a, the negative electrode 12
provided with the gel electrolyte layers 14, and the separator 13b
are sequentially stacked in that order and wound to form a battery
element 10. Then the battery element 10 is placed in the recess
(space) 17a in the laminate film 17 to obtain a gel nonaqueous
electrolyte secondary battery.
[0125] In this embodiment, as shown in FIGS. 1, 3A, and 3B, the
battery element 10 is packaged with the laminate film 17 described
above and the periphery of the battery element 10 is melt-bonded
and sealed to obtain a battery 20. After the battery element 10 is
housed and sealed with the laminate film 17, two side portions
(also referred to as "side sealing portions" hereinafter) 17b of
the recess 17a housing the battery element 10 are bent toward the
recess 17a, as shown in FIGS. 3A and 3B.
[0126] The bending angle .theta. is preferably in the range of
80.degree. to 100.degree.. At a bending angle less than 80.degree.,
the side sealing portions 17b at the two sides of the recess 17a
are excessively open and this increases the width of the battery 20
and makes it difficult to reduce the size of and improve the
battery capacity of the battery 20. The upper limit value,
100.degree., is the value defined by the shape of the recess 17a.
When the battery element 10 housed has a flat shape, the upper
limit value of the bending angle is about 100.degree.. The width
taken for thermal melt bonding at the side sealing portions 17b is
preferably 0.5 to 2.5 mm and more preferably 1.5 to 2.5 mm.
[0127] The bending width D of the side sealing portions 17b is
preferably equal to or more than the height h of the recess 17a or
the thickness of the battery element 10 to reduce the size of and
improve the battery capacity of the battery 20. The number of times
of bending is preferably 1 in order to reduce the size of and
improve the battery capacity of the battery 20.
[0128] Next, an embodiment of a method for producing a battery pack
is described. The battery 20, i.e., the battery 20 including the
battery element 10 packaged with the laminate film 17, the battery
element 10 including the positive electrode 11, the negative
electrode 12, and the separators 13a and 13b packaged with the
laminate film 17, has the positive electrode terminal 15a and the
negative electrode terminal 15b extended to the outside as shown in
FIG. 5. According to the battery pack P shown in FIG. 4, a
plurality of the aforementioned batteries 20 (four in the example
shown in the drawing) are included and electrically connected to
each other through the connecting members 31 to form the battery
group G while the batteries 20 are held together with the holder
33A.
[0129] In the battery pack P shown in FIG. 4, four batteries 20 are
arranged so that their fronts and backs alternate and the positive
electrode terminal 15a and the negative electrode terminal 15b of
adjacent batteries 20 are connected to each other with the
connecting member 31. In other words, four batteries 20 are
connected in series. Then as shown in FIG. 6, the negative
electrode terminal 15b of the battery 20 at one end and the
positive electrode terminal 15a of the battery 20 at the other end
are connected to the protection circuit substrate 32. The
protection circuit substrate 32 controls the voltage and current of
the battery group G that includes the batteries 20.
[0130] Moreover, as shown in FIG. 9A, a holder 33A having openings
34 corresponding to the arrangement of the battery 20 is used in
the battery pack P. The openings 34 shown in the drawing have
shapes corresponding to the cross-sectional faces of the batteries
20 taken in the thickness direction. The holder 33A holds the
batteries 20 together as the batteries 20 are fitted into the
openings 34.
[0131] As shown in FIGS. 10A and 10B, the battery group G and the
protection circuit substrate 32 are placed in a cubic casing
(molding die) C having an open upper end while having the electrode
terminals 15a and 15B and the protection circuit substrate 32
facing upward. Note that although the connecting members 31, the
protection circuit substrate 32, and the holder 33A are omitted
from the drawings in FIGS. 10A and 10B, they are also housed in the
casing C together with the battery group G. During this process,
the holder 33A functions as a positioning unit inside the casing C
and contributes to further improvements of workability and
quality.
[0132] Subsequently, as shown in FIG. 10C, the space in the casing
C housing the battery group G and the protection circuit substrate
32 is filled with a molten resin containing a shape-retaining
polymer, a filler, etc., supplied through a nozzle and the resin is
cured at 100.degree. C. or less to prepare the outer packaging
member 18. As a result, a battery pack P in which the battery group
G, the protection circuit substrate 32, and other associated
components are integrally covered with the outer packaging member
18 is obtained. When the casing C is used as the molding die as in
this embodiment, the casing C can be detached or can be formed as a
part of the battery pack P.
[0133] When a highly viscous resin is used as the resin for forming
the outer packaging member 18, the resin is usually filled by
applying pressure to prevent generation of gaps inside the molding
space in the casing C. During this process, the holder 33A exhibits
a positioning function of keeping the battery group G and the
protection circuit substrate 32 in place against the resin being
filled under pressure. Alternatively, the resin injection may be
divided into two or more operations.
[0134] The battery pack P of this embodiment includes a plurality
of batteries 20 having a volume energy density higher than that of
the battery using a metal can. Even when rectangular batteries 20
having high volume efficiency are used, the dimensional accuracy
and the mechanical strength improve and size and weight reduction
and further improvements of safety and reliability can be
achieved.
[0135] Since the battery pack P has good dimensional accuracy and
mechanical strength and can realize size and weight reduction, the
battery pack P can be used as the batteries for mobile appliances
such as cellular phones, laptop computers, and digital cameras,
secondary batteries for electric and hybrid cars that involve high
output, and batteries for power tools.
[0136] FIG. 7 is a diagram showing another example of a battery
group. The battery group G illustrated in the drawing has four
batteries 20 arranged with the same orientation. The positive
electrode terminals 15a are connected to each other through a
connecting member 31 and the negative electrode terminals 15b are
connected to each other through a different connecting member 31.
In other words, four of the batteries 20 are connected in parallel.
The positive electrode terminal 15a and the negative electrode
terminal 15b of the battery 20 at one end are connected to the
protection circuit substrate 32. In this case, as shown in FIG. 9B,
a holder 33B having openings 34 corresponding to the arrangement of
the batteries 20 is used.
[0137] FIG. 8 is a diagram showing yet another example of a battery
group. In the battery group G shown in the drawing, the positive
electrode terminals 15a of two of the batteries 20 are connected to
each other with a connecting member 31 and the negative electrode
terminals 15b of two of the batteries 20 are connected to each
other with another connecting member 31. Two sets of such batteries
are provided. The positive electrode terminal 15a of one set of the
batteries 20 is connected to the negative electrode terminal 15b of
the other set of the batteries 20 through another connecting member
31. In other words, two of the batteries 20 are connected in
parallel to form a set, and two such sets are connected to each
other in series. Then the negative electrode terminal 15b of the
battery 20 of one set and the positive electrode terminal 15a of
the battery 20 of the other set are connected to the protection
circuit substrate 32. In this case, as shown in FIG. 9C, a holder
33C having openings 34 corresponding to the arrangement of the
batteries 20 is used.
[0138] The holder may be a holder 33D having the openings 34
arranged in columns and rows as shown in FIG. 9D, or a holder 33E
having an opening 34 having a shape corresponding to the front
shape of the main unit of the battery 20 as shown in FIG. 9E.
[0139] The number of batteries 20 included in the battery group G
included in a battery pack may be any instead 4, and series
connections and parallel connections may be freely combined as
desired. Accordingly, the holder for the battery group G may also
take various forms other than those described above illustrated in
the drawings.
[0140] Each of the holders 33A to 33E is housed in a molding die
together with the battery group G etc., as shown in FIGS. 11A to
11C, holds the batteries 20 together, fixes the positions of the
batteries 20 in the die, and is integrally covered with a resin
(outer packaging member 18) filled in the molding die together with
the battery group G and the protection circuit substrate 32.
[0141] The molding die may be a casing C that houses a vertically
disposed battery group G along with the holder 33A as shown in
FIGS. 10A, 10B, 10C, and 11A, or a casing C that houses a
horizontally disposed battery group G along with the holder 33E as
shown in FIG. 11B. The molding die may be constituted by upper and
lower assemble dies D1 and D2 as shown in FIG. 11C or may take any
form without any limitation.
EXAMPLES
[0142] The present application will now be described in further
detail using Examples and Comparative Examples but the present
application is not limited to these examples.
Examples 1 to 18 and Comparative Examples 1 to 3
[0143] Characteristics of the outer packaging member (resin), i.e.,
the types of the shape-retaining polymer and the inorganic filler,
the deflection temperature under load, the glass transition point,
the elongation, and the curing technique (curing temperature), were
varied and battery packs each including a battery group integrally
packaged with a respective outer packaging member were prepared by
using the production method described above. Then the performance
of the battery packs of the respective examples was evaluated.
[0144] Rated energy density (Wh/l) was determined at a temperature
of 23.degree. C. by repeating, for 15 hours at an upper limit of
4.2 V, 1 C constant-current, constant-voltage charging and 1 C
constant-current discharging down to a final voltage of 2.5 V,
where the rated energy density was determined on the basis of the
discharge capacity of the first cycle.
Rated energy density (Wh/l)=(Average discharge voltage
(V).times.rated capacity (Ah))/battery volume
[0145] Note that 1 C represents a current value at which the
theoretical capacity of the battery can be released in 1 hour.
[0146] Each battery pack was subjected to 0.2 C-50 V charging and
0.2 C-30 V discharging and then 1 C charging/discharging was
conducted ten times so that the battery pack was fully charged at
50 V (average voltage: 4.17 V). Then the battery was subjected to a
24 hour vibration test according to JIS D1601. In the vibration
test, each battery pack was placed in a 200.times.200.times.200 mm
casing and fixed with an adhesive tape, 10 g of 50 .mu.m silica
particles simulating sand were placed in the casing, and vibrations
having a frequency of 33 Hz and an acceleration of 10 G were
applied in the horizontal and vertical directions. In the vibration
test, the voltage of each layer of each battery was regularly
monitored through a voltage monitor tab. A battery that included a
layer the voltage of which dropped by 0.05 V or more from the
average voltage of the layer was assumed to be an abnormal battery.
The number of abnormal batteries was recorded and values observed
from such abnormal batteries were excluded from determination of
averages.
[0147] A 720 hour vibration test was also performed. The rate of
change in thickness, visual appearance, and capacity retention
ratio of the most deteriorated battery after 10,000 cycles, and the
maximum temperature observed in an overcharge test were also
investigated. The results are shown in Tables 1 and 2.
TABLE-US-00001 TABLE 1 Deflection Glass Shape- temperature
transition retaining Inorganic under load point (Tg) Elongation
polymer filler (.degree. C.) (.degree. C.) (%) Curing Ex. 1 Acryl
None 58 50 41 100.degree. C. Ex. 2 Epoxy None 152 152 4 100.degree.
C. Ex. 3 Epoxy None 58 55 41 100.degree. C. Ex. 4 Urethane None 156
150 5 100.degree. C. Ex. 5 Urethane None 58 55 40 85.degree. C. Ex.
6 Urethane None 60 55 40 85.degree. C. Ex. 7 Acryl SiO.sub.2 68 64
24 85.degree. C. particles Ex. 8 Epoxy Al.sub.2O.sub.3 132 127 13
85.degree. C. particles Ex. 9 Urethane SiO.sub.2flakes 150 145 13
85.degree. C. Ex. 10 Urethane Al.sub.2O.sub.3 flakes 68 66 24
85.degree. C. Ex. 11 Urethane SiO.sub.2 70 64 24 85.degree. C.
particles Ex. 12 Urethane Al.sub.2O.sub.3 71 66 24 85.degree. C.
particles Ex. 13 Urethane AlN 130 125 13 85.degree. C. particles
Ex. 14 Urethane Si.sub.3N.sub.4 120 114 15 85.degree. C. particles
Ex. 15 Urethane AlN flakes 70 65 22 60.degree. C. Ex. 16 Urethane
Si.sub.3N.sub.4 75 70 18 45.degree. C. flakes Ex. 17 Urethane AlN
105 120 17 45.degree. C. fibers Ex. 18 Urethane Si.sub.3N.sub.4 105
110 17 45.degree. C. fibers C.E. 1 ABS None 130 120 15 120.degree.
C., molten resin extrusion molding C.E. 2 Polyurethane None 120 110
15 110.degree. C., molten resin extrusion molding C.E. 3 None/ None
None None None None polycarbonate resin mold pack No. of No. of
groups of batteries batteries Total Capacity connected connected
No. of Packaging Dimension of unit in series in parallel batteries
material of unit cell cell (Ah) Ex. 1 3 2 6 Al laminate 6E+0.5 3
Ex. 2 4 1 4 Al laminate 6E+0.5 3 Ex. 3 4 1 4 Al laminate 6E+0.5 3
Ex. 4 4 1 4 Al laminate 6E+0.5 3 Ex. 5 4 1 4 Al laminate 6E+0.5 3
Ex. 6 4 1 4 Al laminate 6E+0.5 3 Ex. 7 4 1 4 Al laminate 6E+0.5 3
Ex. 8 4 1 4 Al laminate 6E+0.5 3 Ex. 9 4 1 4 Al laminate 6E+0.5 3
Ex. 10 4 1 4 Al laminate 6E+0.5 3 Ex. 11 4 1 4 Al laminate 6E+0.5 3
Ex. 12 4 1 4 Al laminate 6E+0.5 3 Ex. 13 4 1 4 Al laminate 6E+0.5 3
Ex. 14 4 1 4 Al laminate 6E+0.5 3 Ex. 15 4 1 4 Al laminate 6E+0.5 3
Ex. 16 4 1 4 Two 6E+0.5 3.2 layers: PE film + PET film Ex. 17 4 1 4
Two 6E+0.5 3.2 layers: PP film + PET film Ex. 18 4 1 4 One layer:
6E+0.5 3.3 PE film C.E. 1 4 1 4 Al laminate 6E+0.5 2.7 C.E. 2 4 1 4
Al laminate 6E+0.5 2.8 C.E. 3 4 1 4 Al can 6E+0.5 3 Ex.: Example
C.E.: Comparative Example
TABLE-US-00002 TABLE 2 Failure Failure rate after Average Pack
dimensions Rated E rate after 720 H vibration discharge Thick-
density 24 H vibration test (reference potential ness Length Width
(Wh/l) test test) Ex. 1 3.7 21 92 100 345 Pass: all 20 Fail: all 20
Ex. 2 3.7 27 48 100 343 Pass: all 20 Fail: all 20 Ex. 3 3.7 27 48
100 343 Pass: all 20 Fail: 17 Ex. 4 3.7 26 47 99 367 Pass: all 20
Fail: 13 Ex. 5 3.7 26 47 99 367 Pass: all 20 Fail: 11 Ex. 6 3.7 26
47 99 367 Pass: all 20 Fail: 8 Ex. 7 3.7 26 47 99 367 Pass: all 20
Fail: 8 Ex. 8 3.7 26 47 99 367 Pass: all 20 Fail: 8 Ex. 9 3.7 26 47
99 367 Pass: all 20 Fail: 8 Ex. 10 3.7 26 46 98 386 Pass: all 20
Fail: 7 Ex. 11 3.7 26 46 98 386 Pass: all 20 Fail: 7 Ex. 12 3.7 26
46 98 386 Pass: all 20 Fail: 2 Ex. 13 3.7 26 46 98 386 Pass: all 20
Fail: 2 Ex. 14 3.7 25 46 97.5 400 Pass: all 20 Pass: all 20 Ex. 15
3.7 25 46 97.5 400 Pass: all 20 Pass: all 20 Ex. 16 3.7 25 45 97
434 Pass: all 20 Pass: all 20 Ex. 17 3.7 25 45 97 434 Pass: all 20
Pass: all 20 Ex. 18 3.7 25 45 97 448 Pass: all 20 Pass: all 20 C.E.
1 3.6 27 48 100 300 Fail: all 20 Fail: all 20 C.E. 2 3.6 27 48 100
311 Fail: 11/20 Fail: all 20 C.E. 3 3.7 27 48 100 343 Fail: 12/20
Fail: all 20 Rate of Visual Capacity Maximum change in appearance
retention rate of temperature thickness test after most
deteriorated at overcharge after 10,000 10,000 battery after test
at 50.degree. C., cycles (%) cycles 10,000 cycles (%) 3 C, 100 V
Ex. 1 14 Deformation 62 151 Ex. 2 13 Crack 63 149 Ex. 3 12
Deformation 66 122 Ex. 4 12 Deformation 69 121 Ex. 5 10 Deformation
72 117 Ex. 6 7 Deformation 75 105 Ex. 7 7 Deformation 77 104 Ex. 8
7 Deformation 78 103 Ex. 9 7 Deformation 79 102 Ex. 10 7 Good 81 91
Ex. 11 7 Good 81 90 Ex. 12 7 Good 82 82 Ex. 13 7 Good 82 71 Ex. 14
3 Good 83 70 Ex. 15 3 Good 83 70 Ex. 16 3 Good 83 70 Ex. 17 3 Good
83 70 Ex. 18 3 Good 83 70 C.E. 1 28 Swelling <10 >400 C.E. 2
24 Swelling <10 >400 C.E. 3 31 Swelling <10 >400 Ex.:
Example, C.E.: Comparative Example
[0148] As apparent from Tables 1 and 2, the battery packs of
Examples 1 to 18 achieved better results than Comparative Examples
1 to 3 in terms of 24H vibration test, rate of change in thickness,
visual appearance, and capacity retention ratio of the most
deteriorated battery after 10,000 cycles as well as the maximum
temperature observed in the overcharge test. This confirms that the
battery packs of Examples 1 to 18 all have sufficient mechanical
strength as well as high dimensional accuracy.
[0149] In particular, the battery packs of Examples 10 to 18
maintained excellent appearance and battery packs of Examples 14 to
18 achieved zero failure after 720H vibration test.
Examples 19 to 39 and Comparative Examples 4 and 5
[0150] The resin of the outer packaging member, the endothermic
agent contained in the resin, the type (composition) of the
endothermic agent, the onset temperature of endothermic reactions,
the amount added, and the curing technique (curing temperature)
were varied and battery packs each including a battery group
integrally covered with the respective outer packaging member were
prepared according to the production method above. Then the
performance of the battery packs of the respective examples was
evaluated.
[0151] The rated energy density (Wh/l) was as described above. The
change in dimension after 1 month of storage at 60.degree. C., the
time taken for the inside temperature to exceed 100.degree. C. in
an overcharge test at 50.degree. C., C3, 20 V, and the maximum
temperature in a nail penetration test at 60.degree. C. were
investigated. The results are shown in Tables 3 and 4.
TABLE-US-00003 TABLE 3 Endothermic Type of reaction endothermic
on-set Content Resin Endothermic agent agent temperature (wt %)
Curing Ex. 19 Acryl Nickel hydroxide Metal 247 1 100.degree. C.
hydroxide Ex. 20 Epoxy Cobalt hydroxide Metal 231 60 100.degree. C.
hydroxide Ex. 21 Acryl Zinc hydroxide Metal 205 60 100.degree. C.
hydroxide Ex. 22 Urethane Aluminum hydroxide Metal 175 60
100.degree. C. hydroxide Ex. 23 Acryl Tetrahydrofuran Clathrate 152
1 100.degree. C. hydrate Ex. 24 Epoxy Cyclodextrin Clathrate 88 1
70.degree. C. hydrate Ex. 25 Urethane Aluminum silicate n- Hydrate
148 2 80.degree. C. hydrate Ex. 26 Urethane Copper sulfate 5-
Hydrate 90 40 60.degree. C. hydrate Ex. 27 Urethane Sodium sulfate
10- Hydrate 91 35 60.degree. C. hydrate Ex. 28 Urethane Zirconium
dioxide Hydrate 145 4 80.degree. C. hydrate Ex. 29 Urethane
Aluminum chloride Hydrate 141 4 80.degree. C. 6-hydrate Ex. 30
Urethane Cobalt chloride 6- Hydrate 139 30 80.degree. C. hydrate
Ex. 31 Urethane calcium sulfate Hydrate 137 30 85.degree. C.
hydrate Ex. 32 Urethane Zinc sulfate 7- Hydrate 135 30 85.degree.
C. hydrate Ex. 33 Urethane Nickel nitrate 6- Hydrate 134 10
85.degree. C. hydrate Ex. 34 Urethane Magnesium sulfate Hydrate 133
10 85.degree. C. hydrate Ex. 35 Urethane Gypsum Hydrate 132 10
85.degree. C. Ex. 36 Urethane Calcium sulfate Hydrate 128 15
60.degree. C. hydrate Ex. 37 Urethane Basic zinc carbonate
Carbonate 120 15 45.degree. C. Ex. 38 Urethane Copper hydroxide
Metal 100 15 45.degree. C. hydroxide Ex. 39 Urethane Calcium
sulfite Hydrate 100 15 45.degree. C. C.E. 4 Al can Nickel hydroxide
Metal 247 20 120.degree. C., molten hydroxide resin extrusion
molding C.E. 5 None/ Nickel hydroxide Metal 247 20 280.degree. C.
polycarbonate hydroxide resin mold pack Ex: Example, C.E.:
Comparative Example
TABLE-US-00004 TABLE 4 Change (t in Time taken for inside dimension
after 1 temperature to Maximum temperature in Rated E month of
storage exceed 100.degree. C. in a 60.degree. C. needle penetration
Packaging density at 60.degree. C., 4.25 V 50.degree. C., 3 C, 20 V
test (excluding portions material (Wh/l) (%) overcharge test (sec)
penetrated with needle) Ex. 19 Al laminate 505 9 314 132 Ex. 20 Al
laminate 505 9 312 131 Ex. 21 Al laminate 505 9 311 130 Ex. 22 Al
laminate 505 8 310 129 Ex. 23 Al laminate 505 8 308 128 Ex. 24 Al
laminate 510 7 294 121 Ex. 25 Al laminate 520 5 281 119 Ex. 26 Al
laminate 520 5 279 119 Ex. 27 Al laminate 520 5 278 119 Ex. 28 Al
laminate 520 5 277 119 Ex. 29 Al laminate 520 5 276 119 Ex. 30 Al
laminate 520 4 248 114 Ex. 31 Al laminate 520 4 246 114 Ex. 32 Al
laminate 520 4 245 113 Ex. 33 Al laminate 520 4 244 113 Ex. 34 Al
laminate 520 4 243 113 Ex. 35 Al laminate 520 4 241 113 Ex. 36 Al
laminate 530 3 152 108 Ex. 37 Two layers: 548 2 53 107 PE film +
PET film Ex. 38 Two layers: 555 1 51 106 PP film + PET film Ex. 39
One layer: PE 560 1 47 105 film C.E. 4 Al laminate Battery No cycle
Thermal runaway >400 capacity <10% C.E. 5 Al laminate 480 12
Thermal runaway >400
Ex: Example, C.E.: Comparative Example
[0152] As apparent from Tables 3 and 4, the battery packs of
Examples 19 to 39 achieved better results than Comparative Examples
4 and 5 in terms of changes in dimension after 1 month, time taken
for the inside temperature to exceed 100.degree. C. in the
overcharge test, and maximum temperature in the needle penetration
test. In particular, the maximum temperature in the nail
penetration test was significantly lower than that of the
Comparative Examples 4 and 5, which confirmed that the temperature
suppressing effect of the endothermic agent is significant and the
safety is high.
[0153] It should be understood that various changes and
modifications to the presently preferred embodiments described
herein will be apparent to those skilled in the art. Such changes
and modifications can be made without departing from the spirit and
scope and without diminishing its intended advantages. It is
therefore intended that such changes and modifications be covered
by the appended claims.
* * * * *